Method and apparatus for applying molten metal on strip stock



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Filed Jan. 29, 1941 11 Sheets-Sheet 1 INVENTOR Ceml HMalm TTORNE s Aug. 6, 1946.

METHOD AND APPARATUS FOR APPLYING MOI- TEN METAL ON STRIP STOCK u "U ull IIUU'I C. A. MANN Aug. 5, 1946.

METHOD AND APPARATUS FOR APPLYING'MOL'IEN METAL 0N STRIP STOCK Filed Jan. 29, 1941 11 sheets sheet 2 ESQ INVENTOR Cecz? H Mann a u 7 Z'lwzfaf Aug. 6, 1946. c. A. MANN 2,405,220

METHOD AND APPARATUS FOR APPLYING MOLTEN METAL ON STRIP STOCK Filed Jan. 29, 1941 11 Sheets-Sheet 4 Y INVENTOR Cecil H Mann -vul VII II unvuu nu LHLIIUE D6311)" HUUY' Aug. 6, 1946.

c. A. MANN METHOD AND APPARATUS FOR APPLYING MOLTEN METAL 0N STRIP STOCK Filed Jan. 29, 1941 lllllll Ill Ill llflllllll Ill ilkllllilmll INVENTOR Cec'z? HManzz Y %g%#m c. A. MANN 2,405,220

METHOD AND APPARATUS FOR APPLYING MOLTEN METAL ON STRIP STOCK l1 Sheets-Sheet '7 ah I II I i Nu I NM. aw i K. II T SN. \m\ H l I ma ,4 I. w l \m\ i w R T i %\|v m\ III H II M w T llw r g l .QQK F L INVENTOR- Cec'z'l El. Mann ATTORN Ys Aug. 6, 1946. c, MANN 2,405,220

METHOD AND APPARATUS FOR APPLYING MOLTEN METAL ON STRIP STOCK Filed Jan. 29, 1941 ll Sheets-Sheet 8 3* INVESITOR R Cecil Mann 0 A\1'II'ORNE v v1.41: bil HUU:

t b H In K E F- m o o w m C. A. MANN Aug. 6, 1946'.

METHOD AND APPARATUS FOR APPLYING MOL'IEN METAL 0N STRIP STOCK Filed Jan. 29, 1941 11 Sheets$heet 9 INVENTOR 5851] H wWann MW'QM ATTORNEY$ uuul u" I IUU' Aug. e, 1946. c. A. M-AQN 2,405,220

METHOD AND APPARATUS FOR APfLYING MOLTEN METAL ON STRIP STOCK Filed Jan. 29. 1941 11 Sheets-Sheet 10 \\,sm 51%! j j a i N M:

l- E i i1 m 2 N J h w [Q INVENTOR Cecil H Mann Y a 94! 7 'ATTORNE5 aqmi igzimsm I C. A. MANN Aug. 6, 1946.

METHOD AND APPARATUS FOR APPLYING MOLTEN METAL 0N STRIP STOCK Filed Jam 29' 1941 ll SheetsSheet 11 I km N.

km kw INVENTOR Cecz/ HMann WWW ' ,{QAT'roRNEYS bwN Patented Aug. 6, 1946 METHOD AND APPARATUS FOR APPLYING MOLTEN METAL ON STRIP STOCK Cecil A. Mann, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 29, 1941, Serial No. 376,512

24 Claims.

This invention relates to a method and apparatus for continuously applying a soft metal to the surface of a metal strip and is more particularly concerned with a method and apparatus for continuously applying and simultaneously impregnating porous metallic strip with a lower melting point metal.

It is the primary object of this invention to provide a method and apparatus wherein porous strip material, preferably supported by a more dense metal backing, may be continuously impregnated and overlaid with a lower melting point metal so that the overlay s of a predetermined thickness within close limits.

Another object of the invention is to provide a method and apparatus whereby strip material,

such as composite strip material which includes a porous metal layer thereon, may be continuously impregnated and overlaid with a lower melting point metal, wherein the impregnation takes place under vacuum conditions.

In carrying out the above object it is a further object to impregnate and overlay porous strip material in a substantially flat condition thereby eliminating bending the strip material during operations thereon.

A further object of the invention is to provide a method and apparatus whereby a vacuum may be applied to the porous metal layer of strip material, said vacuum being maintained by means of a seal of the impregnating metal in the molten condition.

Another object of the invention is to thoroughly condition the material for impregnation whereby the strip material is fluxed for improving the wetting action of the molten material, said fluxing being carried out by means of a gaseous medium contacting the metallic surface under elevated conditions of temperature. In some cases said fluxing may be carried out by means of a series of rolls of sponge rubber, or the like, whereby liquid is transmitted to the surface of the metal from a reservoir at a point remote therefrom and uniformly distributed on the surface of the metal and when operating upon porous strip, into the pores therebf.

A still further object is to provide a method and apparatus for casting a predetermined thickness of overlay of lower melting point metal on the surface of a metal strip.

In carrying out the above object it is still another object to maintain the desired thickness of molten metal on top of the metal strip by means of rotatable gates which revolve in the direction opposite to the direction of the gravi y flow of 2 molten metal and whose rate of rotation is reater than the rate of fall of the molten metal whereby the molten metal is held in place until solidification occurs.

Another object of the invention is to provide a method and apparatus for casting an overlay of lower melting point metal on a metal strip wherein the forward speed of motion of the strip is regulated so that the cooling rate of the molten metal is such thatsolidiflcation occurs at atime when the thickness of the overlay reaches a predetermined dimension. .7

Further objects andadvantages of the present invention will'be apparent from the following description, reference, being, had to the'accomp'any ing drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

Fig. 1 is a view in perspective of one type of apparatus which may be used to continuously impregnate and overlay porous metal strip with a lower melting point metal.

Fig. 2 is a diagrammatic illustration of the apparatus shown in Fig. 1.

Fig. 3 is a cross sectional view of the enclosed portion of the apparatus shown in Fig. 1, without showing detailed constructural features.

Fig. 4 is a detailed cross sectional view of the portion of Fig. 3 identified as A."

,Fig. 5 is a view taken on line 5--5 of Fig. 4.

Fig. 6 is a view taken on line 6-6 of Fig. 4. Fig. 7 is a view taken on the line 1--| of Fig. 4. Fig. 8 is a view in section of the enclosed portion of the apparatus identified as C in Fig. 3, together with a cross section of the casting gate.

Fig. 9 is a view taken on the line 9-9 of Fig. 8 showing detailed valve construction.

Fig. 10 is a view taken on the line Ill-l 0 of Fig. 8 showing a cross sectional view of the casting equipment.

Fig. 11 is a view taken on the line li-II of Fig. 8 showing cross sectional view of the outlet gate.

Fig. 12 is a plan view of the casting gate and casting apparatus.

Fig. 13 is a view taken on the line lit-l3 of Fig. 12 and shows in section one of the pairs of rollers used to maintain the strip in alignment.

Fig. 14 is a view taken on the line lL-ll of Fig. 12 showing constructural details of the movable side walls of the casting equipment.-

Fig. 15 is a view taken on the line l5l5 of Fig. 14.

Fig. 16 is a plan view of another embodiment of the castingapparatus.

3 Fig. 17 is a view taken on the line ll-l'l of Fig. 16.

Fig. 18 is a view taken on the line 18-18 of Fig. 16.

Fig. 19 is aview taken on the line l9-l9 of Fig. 18.

Fig. 20 is a view taken on the line tit-26 of Fig. 16.

Fig. 21 is a view taken on the line 2l--2l of Fig. 17.

Fig. 22 is a view in perspective of the gaseous fiuxing apparatus used at the entrance to the enclosed portion of the apparatus.

Fig. 23 is a view in section of the fluxing equipment shown in Fig. 22.

Fig. 24 is a view partly in section of another embodiment of the fluxing apparatus used in connection with a liquid flux.

Fig. 25 is a view taken on the line 25-25 of Fig. 24.

Fig. 26- isa fragmentary viewof fluxing equipment using the resistance of the strip as a means of heating same, and,

Fig. 27 is another view of fluxing equipment utilizing inductive heating.

The apparatus and method disclosed herein is particularly adapted to the application of a low melting point metal upon metallic strip material wherein the strip continuously passes through the apparatus. The apparatus further is adapted to vacuum impregnation of the strip material and thus various materials may b passed therethrough in strip form and be impregnated with any desirable impregnant which, in the preferred form, is a low melting point metal, for example, a lead or tin base Babbitt or other metal having a melting point lower than the melting point of the strip material being operated upon whereby the impregnant may be maintained in a molten condition without changing the phase characteristics of the strip passingtherethrough.

In the preferred embodiment, the apparatus and method is particularly directed to the continuous impregnation of porous metallic material preferably bonded to a strong steel supporting strip. The method of making such porous metal bonded to strip material is clearly disclosed in Koehring Patents 2,198,253 and 2,198,254 whereas material having a porous metal layer bonded to a strong metal backing, said layer being overlaid with a soft metal is disclosed in the Boegehold Patent No. 2,198,240. All of these patents are assigned to the assignee of the present invention. Material as disclosed in the Boegehold patent is particularly desirable in the manufacture of bearings since this stock has the desirable babbitt quality at the surface thereof due to the overlay and likewise has th babbitt layer mechanically locked to the steel by means of the intermeditae porous metal layer. Furthermore, the porous metal layer may be in itself a metal of good bearing characteristics and if the overlay of babbitt should wear through in spots the exposed porous metal will not in any way impair the bearing quality of the element.

In making bearings of the Boegehold type it is particularly desirable from the economy angle to be abl to manufacture the stock of said bearings in a continuous manner. Continuous impregnation and overlaying of a porous metal layer on the steel backing presents a diflicult problem since the steel is of a substantial thickness and is not adapted to excessive bending duing the processing thereof. For this reason it is desirable to impregnate and overlay the porous metal layer with a soft low melting oint metal in the flat condition and it is to this operation that the present method and apparatus is particularly adapted.

In order to clarify the operation of the apparatus a schematic drawing, in section, is shown in Fig. 2, wherein a machine 20 comprises an elon gated tunnel-like structure which is divided into three chambers 24, 26, 28. Strip material 30 enters the apparatus 20 through an opening into chamber 24, then passes through chamber 26 and then through chamber 28. A pair of pinch rolls, not shown, may be used to pull the strip through the machine. Chambers 24 and 28 contain molten low melting point metal in suflicient quantity to cover the strip 38 passing therethrough, while chamber 26, which is intermediate chamber, is evacuated. A reducing gas is preferably maintained over the molten low melting point metal in the chambers 24 and 28 to prevent oxidation of the molten metal. In order to maintain a vacuum in chamber 26 a vacuum pump, not shown, is attached to the pipe 32. A heated supply sump 34 is provided wherein a constant. level of low melting metal in the molten state is preferably maintained and which is connected to the chamber 26 by means of a tube 36 which is immersed in the metal of sump 34 and which connects at the other end thereof to the vacuum chamber 26. The tube 36 should be of greater length than the height of a barometric head drawn on the metal in sump 34. This barometric head is indicated in Fig. 2 and depends upon the density of the low melting point metal. v

A melt-down tank 38 is also provided which may be heated by suitable means and in which a supply of low melting point metal is placed and kept in a molten condition. Since no reducin atmosphere is maintained over this molten metal it is desirable to have a layer of bentonite or other suitable material floating thereon to prevent contact and resulting oxidation by the atmosphere. Two pumps 48 and 42 are provided adjacent the bottom of the melt-down tank 38 and have their outlets connected to the chambers 24 and 28 respectively. These pumps supply suflicient molten low melting point metal to chambers 24 and 28 so that there is always an excess of the molten metal flowing over the weirs 44 and 46, which excess metal passes through pipes 48 and 58 back into the melt-down tank 38.

The vacuum operation of the apparatus depends upon the pumps 40 and 42 having sumcient capacity to maintain a continuous flow of molten metal over the weirs 44 and 46. Thus, as metal leaks out of chambers 24 and 28, either at the outlet or exit of the apparatus, or through the apertures in the two chambers which connect to the vacuum chamber 26, it maintains a vacuum seal at all openings. The metal which flows into the vacuum chamber 26 passes into the pipe 38 where the barometric head is maintained. Excess metal in the sump 3 is eliminated by an automatically operated pump 52, which pumps molten metal from the sump into the melt-down tank to maintain the desired level of molten metal in the sump 34. Thus, the vacuum pump draws a vacuum in chamber 26 which is sealed by metal leaking therein from chambers 24 and 28, and due to the fact that pumps 40 and 42 supply an excess of metal to chambers 24 and 28, the vacuum is never broken and the seal is maintained. In this manner the strip 38 with the porous metal layer thereon passes into the apparatus and is immersed in the molten low melting point metal in chamber 24 whereupon the molten metal par tially impregnates the pores of the porous metal layer but due to occluded air therein does not completely fill the pores. The strip next passes into vacuum chamber where the air pressure over the strip is reduced to such an extent that the occluded air within the pores of the porous metal layer escapes through the molten metal. A vibrator 54 may be used to aid in dislodging the occluded air if desired at this point. After the occluded air is removed from the porous metal the molten metal thereon sinks into the pores. The strip then passes into the next chamber 28 where additional molten metal is supplied as an overlay. From chamber 28 the strip passes through a suitable casting gate I28, to be described in detail hereinafter, where a predetermined thickness of overlay is cast on to the surface of the strip.

Fig. 3 shows a section through the apparatus 20 wherein the detailed construction of chambers 24, 2E and 28 is shown. It will be noted that the three chambers are aligned and are defined by separating walls 58 and 60 which separate chambers 24 and 28 respectively from chamber 26. Each chamber is heated by its own heating unit which preferably is a gas flame burning in tubular combustion chambers 62, 64, 66 and 68. The strip 30 passes from one chamber to another through the various walls including walls 58 and 60 and through throat portions I0 and 12 which are in separating walls 58 and 60 respectively. These throat portions will be explained in more detail hereinafter. The strip 30 when passing through the vacuum chamber 26 goes through perforated tubular receptacles I4 and I6 which act as guides for the strip and which are open adjacent the center of the chamber 26 to permit any excess low melting point metal to drain therefrom. It will be noted that the tubular receptacles I4 and 1e are sloped to insure drainage therefrom. The heaters 64 and 66 in chamber 26 maintain the temperature within the chamber above the melting point of the low melting point metal so that air may be drawn from the interstices of the porous metal layer by the vacuum in the chamber. All the chambers are jacketed by means of an insulated jacket I8. The space between jacket I8 and the walls of chamber 24, 26 and 28 may be filled with heat insulating material or may be a substantially dead air space to prevent transmission of heat. The melt-down tank 38 is also double walled having a heat insulating outer wall 80 enclosing the same.

The detailed construction of chamber 24 is shown in Fig. 4 wherein the heating element 62 is disposed in a serpentine path therein to provide the sections as shown in the drawings. A section through the throat I0 is shown in Fig. 7 wherein the close fit between the strip and the throat may be noted. In. this manner a minimum of low melting point metal is allowed to be drawn through the throat in the vacuum chamber 26. The throat I6 is carried by elongated tubular members 84 which in turn connect with outer throat portion 86 which is bolted to the outer side of the end face of chamber 24. Thus when varying size strips are to be operated upon, the throats may be changed so as to insure a close fitting restriction in the wall between chambers 24 and 26. The entire throat assembly, as will be observed, can be removed by removing bolts 88 and 90 on the outside of chamber 24 and drawing the assembly which includes portions 85 and 10 and connecting tubular members 84 from the chamber 24. A new throat assembly may be i serted by reversing the operation and bolting the assembly in place.

The bottom 92 of chamber 24 is designed to slope toward drain 94 which connects with pipe 96 coming from the pump 40. Thus when it is desired to partially fill the chamber with molten metal the pump 40 is started to pump molten metal through the drain 94 and into the chamber 24 toa level of the weir 98, as shown in section in Figs. 5 and 6. When the level of the metal in chamber 24 exceeds the height of the weir 98 in drains thereover into the sloping channel 99 and returns to the melt-down tank through pipe I00. A window I 02 may be provided in the chamber so that internal operations may be clearly observed.

After the strip has passed through chamber 24 and through vacuum chamber 26 wherein air is substantially removed from the interstices of the porous metal, it next passes into the third chamber 28. Chamber 28 has a removable throat assembly similar to the one used in chamber 24 which includes a restriction I04 in wall 60, connecting members I06, together with a second throat portion I08 in the end wall of the chamber. The throat I08 is shown in detail in Fig. 11 and includes a series of serrated portions IIO which permit a limited amount of metal to flow out on top of the strip. The serrations IIO may be varied to give the desired results. The chamber 28 includes the heater 68 and a lower outlet I I2 which is used to either drain or fill the chamber 28 up to the level of the weir II4 which level is adjustable in height so that a fixed level of the molten metal may be maintained above the surface-of the strip. In this manner, no excessive pressure head is imposed on the metal to increase the flow thereof through serrations H0 in throat I08.

Adjustment of weir I I 4 is obtained by the rotation of hand wheel II6 which rotates the semicylindrical weir level H8 in receptacle I20. The weir level H8 is of the length equal to the length of the weir and rides in the receptacle I20. Rotation of the hand-wheel H6 to the right causes the weir to rotate in a clockwise direction for lowering the level of metal above the strip; whereas rotation of thewheel H6 in the opposite direction makes it possible to raise the level of the metal above the strip. Excess metal which flows over the weir II4 falls into the elongated sloping chamber I22 which is connected by means of pipe 50 with the melt-down tank 38.

When it is desired to completely drain the chamber I22 the. hand wheel I24 may be used which connects with a valve I26 that permits any excess metal in the chamber I22 to drain back into chamber 28 whence it will flow through the lower drain II2 back into the melt-down tank when the pump 42 stops operating. It is desirable when draining either chamber 24 or chamber 28 to remove the pumps or open the passageway therethrough so that metal in either chamber may be drained completely back to the meltdown tank. Longitudinal walls 91 and H3 cooperate with weirs 98 and I I4 respectively to re duce the volume of chambers 24 and 28 thereby reducing the required quantity of molten metal in each chamber.

After the strip emerge from chamber 28 through the throat I08 it passes into the casting apparatus or what may be termed casting gate I28 which is shown in section in Fig. 10 and which includes a rotatable wire brush I30 that is placed close to the throat I08 and beneath the springs I34, the construction by weir H4 are all strip to remove any low melting point metal from the back side of the strip 30. The top of the strip due to the serrations H in throat I08 carries an overlay of molten metal which is held in place by side rails I32 as shown in the plan view Fig. 12. These rails are spring pressed against the side of the strip by a plurality of thereof being clearly noted in Fig. 15. The rails are serrated at the sides thereof opposite to the sides that contact the strip, as at I36, for keeping the rails heated at the outer edges thereof, the heat being transmitted to the serrations by longitudinal gas burners located beneath the side rails I32. The springs I34 are et in recesses I38 of blocks I40,

' which blocks are water cooled by means of circulating water supplied through pipes I42 which passes through chambers I44 in blocks I40.

In order to keep the strip 30 substantially level in a given plane two leveling plates I46 are used which are likewise resiliently held, as shown in Fig. 14- by means of springs I48, in engagement with the surface of strip 30. The plates I46 are pivotedly attached to blocks I40 by bolts I41 whereby tilting of the plates is possible around the bolts against the compression of springs I48. Thus the rails I32 and leveling plates I46 keep the strip in alignment while it passes through the casting gate I28.

In order to permit the use of varying width strips as 30, the side rails I32 are adjustable laterally. The adjustment is accomplished by the turning of handle I66 which causes screws I68 and I to turn which screws are threaded on one end thereof with right-hand threads and On the other end thereof with left-hand threads whereby the hangers I12 of blocks I40 travel inwardly or outwardly in accordance with the direction of rotation of the handle I66. In this manner major adjustments for width may be accomplished since translation of the block I40 in either direction obviously moves the side rails and other supported mechanisms therewith.

The side rails I32 are maintained at a temperature above the melting point of low melting point metal in order to prevent premature freezing thereof and resultant sticking of the strip thereto. Referring to Fig. 14, the channeled construction at the interior. of block I40 is shown wherein the longitudinal chamber I14 which extends the length of the block is supplied with gas and air under pressure. This chamber communicates with the longitudinal opening I16 in the block at spaced distances through hollow bolts I18. These bolts supply air and gas to a burner I80 which runs longitudinally in opening I16 and burns beneath the side rails I32 to maintain the same at any predetermined temperature. The block I40 also carries a pair of longitudinal channels or chambers I82 and I84 therein which are used as a means for circulating water therethrough to keep the block cool so that the temper of the various springs received therein is not removed. Fuel is supplied to the burners I80 through tubes I86 connecting with the proper channel in block I40 while the water connections I42 connect in the water supply pipe I88.

The slightly inclined plane at which the strip 30 passes through the casting gate, the speed of the strip, the size of the serrations in the throat I08, and the level of the molten metal maintained factors controlling the thickness of the low melting point metal to be cast on the surface of the strip 30. In order to set the molten metal on the strip as it passes through the gate I28 a plurality of water jets I50 are used which direct stream of water against the underside of the strip just after it emerges from the side rails I32. This freezes the molten metal at this point. In order to prevent any sticking as the strip passes the end of the rails I32 in the event that the freezing should be slightly premature, two gas burners I52 are provided which heat the corners of rails I32 as the strip 30 passes therefrom. At the other end of the casting gate I28, two sets of rollers are provided, the upper pair being designated as I54 whereas the lower pair is designated as I55. These rollers help guide the strip as it passes this point. All four rollers are journaled on ball bearings I56 and each of the upper pair of rollers I54 is rotatably mounted on a shaft I58 and is urged by means of spring I60 toward the strip 30. In this manner a definite pressure is maintained on the strip at all times to aid in guiding the same. The pressure of spring I60 may be adjusted by means of screw I6I to vary the pressure of the rollers I54 on top of the strip 30. The strip 30 passes out of chamber 28 at a slight upward angle and, therefore, as it passes through the casting gate it is possible to maintain the depth of metal on the strip at any desired depth prior to freezing thereof by suitable adjustment of the speed of the strip and the size of the serrations H0 and by the degree of the angle of the strip.

A second embodiment of a suitable casting gate is shown in Figs. 16 through 20. Referring particularly to Fig. 16, a pair of longitudinally spaced rollers I90 are disposed on either side of the strip 30 and rotate in the direction of the arrows as shown in Fig. 1'7. These rolls I90 are cored out and include therein a plurality of inwardly extending projections I92 to increase the inner surface of the roll. Each of the rolls is provided with a ga burner to heat the interior thereof and thereby cause the exterior to reach a sufficiently high temperature to prevent freezing of the molten metal thereto. These burners are supplied gas through pipe I94. The rolls I90 are driven by a motor I96 through suitable gearing, as shown in Figs. 18 and 19 at I98. In this manher, the rolls may be caused to rotate at any desired speed but in opposite directions. The proper rate of rotation may be obtained by observation. Thus the rolls I90 rotate at a speed sufilcient to overcome the attraction of gravity toward the molten metal and thereby prevent the metal from leaking through the small longitudinal spaces between the edges of the strip and the rolls. In this manner, the molten metal is held on top of the strip between the rolls. In order to maintain a predetermined depth of molten metal, a third roll 200 is provided which is set in a plane transverse to the plane of movement of the strip 30, This roll is of larger diameter than rolls I90 and is cored out in a similar manner at the interior thereof to produce a plurality of inwardly extending projections 202. The roll 200 is suitably journaled as at 254 and 206 and is set directly above a somewhat similar roll 208 that is placed beneath the strip. The roll 208 has circumferential grooves at the surface thereof as at 2I0. This roll is also hollowed out at the interior thereof. The rolls 200 and 208 are geared as at 2I2 and therefore rotate in synchronism when driven by a motor 2I4 through a chain drive 2I6. The roll 200 has a gas burner 2 I 8 disposed therein which maintains the roll in a heated condition. The journals 204 and 206, which support the roll 200, have suitable brackets thereon which are hinged to the casting gate framework by means of auxiliary shafts as shown at 219 in Fig. 20. The roll 200 is thus rotatable on the shafts 2| 9 and may be adjusted to any desired distance above the strip by means of indexing nuts 220 which act through ball thrust bearings 224 so as to be easily rotatable on rod 222 for adjustment purposes. Obviously, if any irregularities occur on strip 30 the upper roll 209 is capable of upward movement on shafts 219 to permit such irregularities to pass thereunder.

The roll 290 rotates in the direction of the arrows in Fig. 21 and the speed of the rotation is such that excess molten metal on the strip is prevented from passing thereunder. In this manner, the metal which remains on the strip is of a definite thickness as it passes through rolls 200 and 298.

Beneath the strip and just before the strip passes beneath roll 29!], see Fig. 21, a water jet 226 is provided to start solidification of the molten metal. This jet, however, does not cool the strip sufliciently to actually freeze said metal but merely reduces its temperature to a point somewhere near freezing. After passing between rolls 200 and 298, a second jet 228 is provided which causes final solidification or freezing of the metal. The jets 226 and 228 are connected to a Water source supplied by pipe 236. Since rolls I90 are heated the strip does not freeze thereto regardless of where the freezing of the low melting point metal occurs and, therefore, is free to pass from the casting gate.

When operating on varying width strips 30 the side rollers I99 may be adjusted by means of handle 230 which acts through suitable gears to turn the threaded rods 232 and 234 which carry the rolls I99. Since each rod carries a right and a left-hand thread thereon it is possible to cause the rolls I99 to either come closer together or to move further apart in accordance with the width of the strip 30 to be operated upon. In the present embodiment varying width strips require complete change of rolls 299 and 208 to rolls of the desired width. The circumferential grooves 2) on roll 298 are cast therein to prevent overheating of the roll and permit free air fiow beneath the strip, A hood (not shown) may be provided over the strip 30 and closely fitted to the contour of the rollers I90 and 209 into which a non-oxidizing atmosphere may be introduced. This hood may or may not be desirable according to the oxidation of the soft metal, in other words. if the metal is not excessively oxidized the hood need not be used.

When operating on metal strip material it is usually desirable to clean the same and remove oxide coatings, etc., so that low melting point metal wets the surface as the strip passes through the apparatus. This step may be termed a fluxing step and while fiuxing equipment is provided with the present apparatus it should be understood that in cases where strip metal is provided that is free from oxide that such fluxing apparatus or'step may be unnecessary. However, under usual production conditions it is advisable to have the fluxing step included in the process. Referring to Fig. 22, the preferred type of fiuxing equipment 249 is shown. This fluxing equipment includes a gas burner 241 which comprises a cored out block 242 which carries therein a plurality of blast burners 244. The block 242 is connected to an air-gas supply through a pipe 246. Additional outlets in the block, such as 248. are also provided so that when varying width strips are 10 used additional burners may be inserted. These openings 248 may be plugged when not in use. The strip 39 passes over the burner 2M and is heated to a suitable elevated temperature but below its melting point. Prior to its entry into the apparatus through the throat 83, a hood 250 is provided which is hollowed out as noted in Fig. 23 and is connected by means of the pipe 252 to a source of a reducing atmosphere. Thus as the strip 30 in the heated condition passes beneath hood 259 it is subjected to the action of a reducing atmosphere, such as; hydrogen, carbon monoxide, mixtures thereof, incompletely burned natural gas, or any other suitable reducing atmosphere. Thus the action of the atmosphere on the oxides at the surface of the strip causes the reduction thereof which is hastened by the heated condition of the strip. Likewise certain other foreign material that is detrimental to bonding is removed due to the heat. In this manner, the strip 39 as it passes through the throat 86 is preheated and likewise is cleaned of all oxides and certain other foreign matter and is thereby fluxed so that the molten metal in the chamber 24 readily wets the surface thereof.

The fiuxing equipment as shown at 240 is particularly successful first, because the strip is preheated and, second, because the metal of the strip is in what might be termed a nascent condition due to the reducing action just prior to the immersion into the molten metal. In this manner, the molten metal appears to have a better wetting action than under any other known conditions.

Another type of fluxing equipment shown in Figs. 26 and 27'utilizes electrical heating of the strip. In this instance the strip 30 as shown in Fig. 26, passes between a pair of pinch rolls 215 and 211 which are spring pressed by means of springs 216 and are carried by block 219'which is supported by and insulated from a support 28I. The block 219 is connected to one side of a suitable electrical current source by means of a conduit 283. The hood 250 is similar to the hood shown in Fig. 23 and is supplied with reducing gas through tube 252. The strip 30 passes into the babbitt designated at 285 which is carried within chamber 24. The babbitt and chamber are connected to the other side of the current source by means of the conduit 281. Thus a complete circuit is set up through conduit 283, block 219, pinch rolls-215, strip 30,'babbitt 285 and conduit 281 whereby the portion of the strip between the pinch rolls 215 and 211 and the babbitt 285 is heated by means of the resistance thereof to a suitable temperature. This temperature can be varied by either changing the current input, or by increasing the distance between the pinch rolls and the babbitt 285 In this manner, the strip is heated to a temperature approximating the temperature obtained when using the apparatus as shown in Fig. 23 and reducing gas is held thereover by hood 259. Thus the apparatus fluxes the surface of the strip and cleans the same of any oxidation.

Fig. 2'1 shows another modification of the electrically heated equipment wherein the strip 39 passes through an elongated tunnel 291 which includes an insulating outer portion 293 and a coil 295 therein which is connected by means of conduits 291 and 299 to a suitable current source. As the strip 30 passes through the coil, it is heated inductively to a suitable temperature. Reducing gas is supplied chamber 29| from tube 301 and fluxes the strip in the same manner as previously 11 described in connection with Figs. 22, 23 and 26. Resistance and inductive heating are well-known in the art and, therefore, specific currents etc., will not be designated since these factors are best arrived at by trial and in accordance with the width, thickness and length of strip used.

A second type of fiuxing equipment is shown in Figs. 24 and 25 where no preheating of the strip 30 is involved. In this embod ment a series of sponge rubber rolls 254, 255 and 256 are disposed in driving relation to one another with the roll 256 dipping into a fiuxing liquid 258 held in a shallow tank 260 and with the roll 254 bearing against the surface of the strip 30. Thus, as the strip progresses in the direction of the arrow the roll 254 is rotated and drives the rolls 255 and 256 due to their frictional engagement, As theroll 25B rotates it picks up liquid flux from the tank 250 and this flux is transferred from roll 256 to roll 255 to roll 254 whence it is evenly spread on the surface of the strip 30. Suitable valve equipment 262 with a fioat 265 maintains the level of the flux 258 in tank 260 by supplying additional flux from a main supply tank 266. Any suitable fiux may be used such as zinc chloride, "Blanc liquid or any other commercial fiux which will give the desired results.

The present method and apparatus eliminates one of the major problems in continuous vacuum impregnation of the strip material, namely, the bending of the material. In the present instance the strip passes through the apparatus in a substantially fiat condition and the vacuum is maintained through the use of pumps which supply molten metal in sufficient quantities to maintain the vacuum seals and likewise maintain a definite level of molten metal above the surface of the strip. I am aware of the past type of impregnating apparatus for use in vacuum impregnation wherein the conventional type of barometric leg is utilized and wherein the strip must be bent and passed upwardly through an impregnant column equal to the barometric head and then passed downwardly through another column of similar height. Such procedure is unnecessary when following the present method and by using the present apparatus.

Another feature of this invention resides in the casting gate apparatus wherein a defined thickness of low melting point metal may be cast upon the surface of a strip in a continuous manner. Obviously this casting gate may be used whether or not the vacuum impregnation is utilized since it is possible to cast one metal upon the surface of another in this manner whether or not a D- rous metal layer is used. Similarly, the fluxing arran ement may be used with any other type of impregnating or casting equipment to yield equally satisfactory results.

Embodiments of the casting gate as shown in Figs. 16 through 21 utilizes a widely different principle of operation than the gate as shown in Figs. 8, 10, 12 through 15. In the first instance the level of molten metal is maintained by overcoming the force of gravity whereby the molten metal is prevented from dropping off the surface of the strip through the use of rotating mechanisms whose rotational speed in feet per minute is greater than the rate in feet per minute of gravity fall of the molten metal. In this manner the molten metal is maintained at a definite level on the surface of the strip until freezing occurs. In the second embodiment the thickness of the molten metal held on the surface of the strip is controlled by the rate of speed of the strip, the

12 opening in the throat I08 and by the cooling rate of the strip. Either type of apparatus provides satisfactory results although for adjustment reasons it is apparent that the second type of gate is more practical from a production angle where various width strips are necessarily operated upon in a single machine.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A vacuum impregnating apparatus for use in the continuous impregnation of metallic strip material which includes a porous metal layer thereon, comprising; an elongated tunnel-like structure having openings at both ends thereof to permit ingress and egress of the strip, said structure including, a chamber at the ingress end thereofadapted to be partially filled with babbitt in the molten condition through which the strip passes, an intermediate chamber which is adapted to be evacuated and which connects with said first chamber by means of a throat that fits closely around the strip, and a third chamber at the egress end of the structure adapted to be partially filled with babbitt through which said strip passes and having a throat that fits closely around the strip at the ingress end thereof, means for evacuating said middle chamber; a supply tank filled with molten babbitt, and pump means adapted to pump molten babbitt into each of said end chambers, said pump means havin sufiicient capacity to maintain the level of babbitt in said two end chambers above the surface of the strip whereby the molten babbitt seals said two end chambers from said vacuum chamber, said two end chambers and said vacuum chamber together with the ingress and egress openings and the communicating throats being so disposed with relation to one another that the strip material passes therethrough in a single plane.

2. An apparatus for continuously impregnating metallic strip material including a porous metal layer thereon, said material being in a substantially fiat condition during the impregnation thereof, comprising in combination; a babbitt chamber adapted to be partially filled with babbitt through which said strip may pass and including throats at either end thereof which closely fit the strip as it passes into and out of said chamber; a communicating chamber at the egress end of said first chamber means for evacuating said second mentioned chamber; a third chamber at the egress end of said second chamber and including throat portions at either end thereof, said third chamber also being at least partially filled with molten babbitt; a heated supply tank for holding a large supply of molten Babbitt metal therein; pump means connected with said supply tank and with said first and third mentioned chambers for maintaining the level of babbitt in said first and third chambers substantially constant and above the surface of the strip, whereby the babbitt maintains a. vacuum seal at the egress end of said first chamber of the ingress end of said second chamber; and return means connected with said first, second and third chambers for returning excess babbitt to said supply tank.

3. An apparatus as claimed in claim 2 wherein weirs having their edges longitudinally disposed above the level of the strip are provided in said first and third chambers to maintain the desired level of ba bitt therein.

4. An apparatus as claimed in claim 2 wherein heating means are included in said first and third chambers for maintaining the babbitt in a molten condition.

5. An apparatus as claimed in claim 2 wherein said first chamber includes a fixed longitudinal weir disposed above the level of the strip for maintaining a defined level of babbitt therein and wherein said third chamber includes an adjustable longitudinal weir normally disposed above th level of the strip whereby the babbitt level in said third chamber may be maintained at any desirable depth.

6. In a machine for continuously impregnating porous strip material in the substantially fiat condition, an impregnating chamber including throat portions at either end thereof for restricting the flow of impregnant therefrom around a strip passing therethrough, a communicating vacuum chamber at the egress end of said first chamber, means for evacuating said vacuum chamber, and a second impregnating chamber connected with the egress end of said vacuum chamber and including throat portions at either end thereof for restricting the flow of impregnant therefrom around a strip passing therethrough, a supply tank for the impregnant, pump means for pumping impregnant to each of said impregnating chambers said pump means having sufficient capacity to maintain a defined level of impregnant in each of said chambers above the level of said strip regardless of the leakage into the vacuum chamber and out of the machine, and return means for returning the impregnant which leaks out of said throat portions to said supply tank.

7. An apparatus for continuously casting a layer of a low melting point metal upon the surface of a highe point metal strip comprising in combination, a supply tank containing a heated supply of molten low melting point metal through which said strip of higher melting point metal passes, a threat at the egress end of said tank said throat having sufficient clearance to permit a flow of molten metal from said tank onto the surface of said strip, resiliently pressed confining means comprising rails at the sides of said strip for holding said molten metal thereon, means for heating said rails to prevent premature freezing of said molten metal, cooling means disposed beneath said strip and to a point remote from said throat for rapidly cooling the strip and the molten metal thereon for freezing the low melting point metal whereby the thickness of metal cast on said strip is controlled by means of the speed of the strip the clearance of the throat and the distance between said throat and said cooling means.

8. In an apparatus for continuously castin a layer of definite thickness of low melting point metal upon the surface of a higher melting point metal strip comprising in combination, a supply tank for molten low melting point metal through which said strip passes, said tank including a throat having a predetermined clearanc therein at the egress side thereof for sa d strip, said strip passing through the supply tank at a slight incline, means adjacent said throat for maintaining the molten metal on the surface of the strip in place after the strip has passed from said tank, and cooling means spaced remotely from said throat and beneath said strip for substantially solidifying the molten metal on said strip at a time when the depth of said molten metal reaches the predetermined thickness of metal desired to be cast on said strip as determined by the in- 14 cline of the strip, the clearance of the throat, and the speed of the strip.

9. An apparatus as claimed in claim 8 which includes a wire brush disposed beneath the strip adjacent the throat for removing excess molten metal from the back of the strip.

10. An apparatus as claimed in claim 8 wherein the means for maintaining the molten metal in place on the strip are heated to a temperature sufiicient to prevent premature freezing thereto.

11. In an apparatus for continuously casting a layer of desirable thickness of low melting point metal upon the surface of a higher melting point strip comprising in combination, confining means adjacent the edges of the strip resiliently held thereto for providing a shallow trough therewith, means for supplying molten low melting point metal to the surface of the strip as the strip passes between said confining means, and means remote from said upply means for cooling the low melting point metal on the surface of the strip for solidifying the same, said cooling means being so spaced from the supply means and the speed of the strip so regulated that the thickness of the solidified low melting point metal layer is the desired thickness.

12. In an apparatus for continuously casting a layer of low melting point metal upon the surface of a higher melting point metal strip comprising in combination, longitudinally spaced confining means resiliently held against the edges of a strip moving at a slight upward incline therebetween whereby a trough is formed between the confining means and the strip, supply means for supplying molten low melting point metal at the low end of said trough, and cooling means disposed remote from said supply means for solidifying the low melting point metal when the thickness thereof reaches the desired thickness.

13. In an apparatus for continuously casting low melting point metal upon the surface of a higher melting point metal strip comprising in combination, supply means for supplying molten low melting point metal to the surface of said strip, means for preventing gravity fiow of said metal from the surface of said strip along both longitudinal edges thereof, means between said first means for controlling the depth of low melting point metal passing thereunder, and cooling means for solidifying the controlled thickness layer of low melting point metal upon the surface of said strip.

14. The apparatus as claimed in claim 13 wherein said means for preventing gravity flow of metal consists of rollers rotating in a direction against gravity fiow at a speed sufilcient to prevent gravity fiow of the molten metal.

15. The apparatus as claimed in claim 13 wherein the means for controlling the depth of molten metal consists of a roller spaced a defiinite distance from the surface of said strip and rotating the speed sufiicient to prevent molten metal from passing thereunder in quantities in excess of the desired quantity.

16. An apparatus for continuously impregnating strip material in a substantially fiat condition, comprising in combination, an impregnating chamber including an inlet and outlet through which said strip passes, said impregnating chamber adapted to contain impregnant so that the strip is covered therewith, a communicating vacuum chamber, means for evacuating said vacuum chamber, a second impregnating chamber oommunicating with the other end of said vacuum chamber and having an inlet and outlet therein through which said strip passes, said second ime pregnating chamber adapted to contain sufficient impregnating material to substantially cover said strip, means for pumping impregnating material in suflicient quantities to said two impregnating chambers to maintain a vacuum seal between said chambers and said vacuum chamber, a supply mean for holding a large supply of impregnating material and connected to said means for pumping the material to said chambers and means cooperating with the inlet and outlet of each of the said two impregnating chambers for returning the impregnant which discharges therefrom to said supply means.

17. An apparatus for continuously impregnating strip material in a substantially flat condition comprising in combination; a three part structure including two impregnating chambers adapted to be filled with the impregnating material to a predetermined level and an intermediate communicating chamber adapted to be evacuated, said strip passing through said three chambers in a substantially flat condition by means of inlets and outlets in said two impregnating chambers, said level of impregnant in said chambers being maintained above the level of the inlets and outlets, means for evacuating said vacuum chamber, a supply means for containing a large supply of impregnant, and separate pump means automatically controlled and disposed between said supply means and said impregnating chambers for maintaining the level of said impregnant in said chambers to the desired height whereby the impregnant lost by leakage from the inlets and outlets of said chambers is compensated for by incoming impregnant for maintaining the vacuum seal between said chambers and the vacuum chamber, and return means for returning the overflow of said impregnant to said supply means.

18. In combination with an apparatus for continuously casting a low melting point bearing metal upon the surface of a higher melting point supporting strip; a chamber through which said strip passes, a weir positioned within said chamber formed in the general shape of a trough for containing molten low melting point bearing metal and having the sides thereof sufficiently high to maintain the surface of said low melting point metal above the strip, one portion of said weir being adjustable longitudinally thereof whereby the level of the molten metal above said strip may be closely controlled so that any depth of the'metal may be maintained.

19. An apparatus for continuously impregnating porous strip material in a substantially flat condition, comprising in combination; an impregnating chamber including an inlet and an outlet through which a strip passes, said impregnating chamber being adapted to contain suflicient impregnant so that the strip i covered therewith, a communicating vacuum chamber, means for evacuating said vacuum chamber, a second impregnating chamber communicating with the other end of said vacuum chamber and having an inlet and outlet therein through which said strip passes; said second impregnating chamber adapted to contain suflicient impregnant to substantially cover said strip, supply means for holding a large quantity of impregnating material, pump means connecting said supply means with each of said impregnating chambers for pumping impregnant from said supply means to said chambers, overflow means in each of said chambers for returning excess impregnant pumped thereto back to said supply means, a Sump below said combination,

supply means and connected with said vacuum chamber, said sump receiving impregnant leaking from said impregnating chamber into said vacuum chamber, and a separate pump means for pumping impregnant from the sump to said supply means for maintaining a given quantity of impregnant in said sump.

20. In an apparatus for continuously casting a layer of low melting point metal upon the surface of a higher melting point metal strip comprising in combination, means for moving the strip in one direction, supply means for supplying molten low melting point metal in defined quantities to the surface of said strip, means for preventing flow of said molten metal from the longitudinal edges of said strip, and cooling means spaced from said supply means for solidifying the low melting point metal on the surface of said strip, the thickness of said solidified layer being dependent upon the speed of the strip and the quantity of molten metal supplied by the supply means to the surface of the strip.

21. In an apparatus for continuously casting a layer of predetermined thickness of low melting point metal to the surface of higher melting point metal strip comprising in combination; confining means longitudinally disposed adjacent the longitudinal edges of a metal strip, means for moving said strip in on direction at a slight upward incline between said confining means, supply means for supplying molten low melting point metal at the lower end of said moving strip, cooling means disposed remot from said supply means for solidifying .the low melting point metal on the surface of said strip when the thickness of said low melting point metal layer reaches adesired thickness, means for maintaining the strip fiat adjacent said cooling means, and heating means for providing localized heating adjacent said last named means for preventing the strip from adhering the last named means while low m lting point metal is solidifying.

22. In an apparatus for continuously casting a low melting point metal upon the surface of a higher melting point metal strip, comprising in longitudinally spaced confining means resiliently held against the edges of a strip moving at a slight upward incline therebetween whereby a trough is formed between the confining means and the strip, supply means for supplying molten low melting point metal at the low end of said trough, heating means for maintaining said confining means at a sufficiently high temperature for preventing solidification of the molten low melting point metal thereagainst, and cooling means disposed remote from said supply means for solidifying the low meltin point metal when the thickness thereof reaches the desired thickness as determined by the incline of th strip and the rate of longitudinal movement thereof.

23. In a method of impregnating porous metal strip material continuously in a substantially flat condition the steps comprising: immersing a flat stiff strip of porous metal in molten metal contained within an impregnating chamber, passing the strip from the molten metal into a vacuum chamber for removing occluded air from the pores thereof, again immersing the strip in molten metal contained within a second impregnating chamber, said strip being maintained in substantially the same horizontal plane throughout all of. said immersing and impregnating steps, and continuously supplyin molten metal to each of said two impregnating chambers in sufficient quantities to provide th sole seal between said 17 chambers and said vacuum chamber whereby said strip becomes impregnated with said molten metal.

24. In. a method of maintaining a vacuum in a mechanism adapted to impregnate porous stifl metal strip material in a substantially flat condition; providing two impregnating chambers containing impregnating molten metal, providing an intermediate vacuum chamber connecting said impregnating chambers, all or said chambers being in substantially the same horizontal plane and so constructed that leakage can occur from said impregnating chambers into said vacuum 18 chamber around said strip, passing said strip through all 01' said chambers in the substantially flat and unbent condition and in a single horizontal plane and beneath the impregnant in said impregnating chambers, pumping suflicient impregnant into each of said impregnating chambers to maintain the level of the molten metal constant so that said impregnant leakage is compensated for by the new impregnant being pumped into said chambers, whereby the vacuum seal is maintained between said impregnating chambers and said vacuum chamber.

CECIL A. MANN. 

